Quick start with dub

dub runs tests with dub test. Unfortunately, due to the nature of
D's compile-time reflection, to use this library a test runner file
listing all modules to reflect on must exist. Since this is a tedious
task and easily automated, unit-threaded has a dub configuration
called gen_ut_main to do just that. To use unit-threaded with a dub
project, you can use a unittest configuration as exemplified in this
dub.json:

Fast compilation mode

Fast compilation mode. Set the version to unitThreadedLight and it will
compile much faster, but with no error reporting and certain features
might not work. Experimental support.

Advanced Usage: Attributes

@ShouldFail is used to decorate a test that is
expected to fail, and can be passed a string to explain why.
@ShouldFail should be preferred to @HiddenTest. If the
relevant bug is fixed or not-yet-implemented functionality is done,
the test will then fail, which makes them harder to sweep
under the carpet and forget about.

Since code under test might not be thread-safe, the @Serial
attribute can be used on a test. This causes all tests in the same
module that have this attribute to be executed sequentially so they
don't interleave with one another.

Although not the best practice, it happens sometimes that a test is
flaky. It is recommended to fix the test, but as a stopgap measure
the @Flaky UDA can be used to rerun the test up to a default number
of 10 times. This can be customized by passing it a number
(e.g. @Flaky(12));

The @UnitTest and @DontTest attributes are explained below.

There is support for parameterized tests. This means running the test
code multiple times, either with different values or different types.
At the moment this feature cannot be used with the built-in unittest
blocks.

For values and built-in unit tests, use the @Values UDA to supply
test values and getValue with the appropriate type to retrive them:

@Values(2, 4, 6)
unittest {
assert(getValue!int % 0 == 2);
}

This will run the test 3 times, and the reporting
will consider it to be 3 separate tests.

If more than one @Values UDA is used, then the test gets instantiated
with the cartesian product of values, e.g.

The test above is instantiated 4 times for each one of the possible
combinations. This helps to reduce boilerplate and repeated tests.

You can also declare a test function that takes parameters of the
appropriate types and add UDAs with the values desired, e.g.

@(2, 4, 6)
void testEven(int i) {
(i % 0 == 2).shouldBeTrue;
}

For a cartesian product, simply declare more parameters and add
UDAs as appropriate.

For types, use the @Types UDA on a template function with exactly
one compile-time parameter:

@Types!(int, byte)
void testInit(T)() {
T.init.shouldEqual(0);
}

The @Name UDA can be used instead of a plain string in order to name
a unittest block.

unit-threaded uses D's package and module system to make it possible
to select a subset of tests to run. Sometimes however, tests in
different modules address cross-cutting concerns and it may be
desirable to indicate this grouping in order to select only those
tests. The @Tags UDA can be used to do that. Any number of tags
can be applied to a test:

@Tags("foo", "tagged")
unittest { ... }

The strings a test is tagged with can be used by the test runner
binary to constrain which tests to run either by selecting tests
with or without tags:

./ut @foo ~@bar

That will run all tests that have the "foo" tag that also don't have
the "bar" tag.

If using value or type parameterized tests, the @AutoTags UDA will
give each sub-test a tag corresponding to their parameter:

The @Setup and @Shutdown UDAs can be attached to a
free function in a module. If they are, they will be run before/after
each unittest block in a composite (usually a module). This feature
currently only works for unittest blocks, not free functions.
Classes could override setup and shutdown already.

Property-based testing

There is preliminary support for property-based testing.
To check a property use the check function
from unit_threaded.property with a function returning bool:

check!((int a) => a % 2 == 0);

The above example will obviously fail. By default check runs the property
function with 100 random values, pass it a different runtime parameter
to change that:

check!((int a) => a % 2 == 0)(10_000); // will still fail

If using compile-time delegates as above, the types of the input parameters
must be explicitly stated. Multiple parameters can be used as long as
each one is of one of the currently supported types.

Command-line Parameters

There is support for debug prints in the tests with the -d switch.
This is only supported in single-threaded mode (-s). Setting -d
without -s will trigger a warning followed by the forceful use of
-s. TestCases and test functions can print debug output with the
function writelnUt available here.

Tests can be run in random order instead of in threads. To do so, use
the -r option. A seed will be printed so that the same run can be
repeated by using the --seed option. This implies running in a
single thread.

Integration tests and a sandbox environment

If you want to write tests that read from and write to the file system,
you can use the Sandbox struct from
unit_threaded.integration like so:

By default the sandbox main path is tmp/unit-threaded but you can change
that by calling Sandbox.setPath

Test Registration and Test Runner

There are two example programs in the example folder,
one with passing unit tests and the other failing, to show what the
output looks like in each case. Because of the way D packages work,
they must be run from the top-level directory of the repository.

The built-in D unittest blocks are included automatically, as seen in
the output of both example programs
(example.tests.pass_tests.unittest and its homologue in
example_fail). A name will be automatically
generated for them. The user can specify a name by decorating them
with a string UDA or the included @Name UDA.

The easiest way to run tests is by doing what the example code does:
calling runTests() in runner.d with
the modules containing the tests as compile-time arguments. This can
be done as symbols or strings, and the two approaches are shown in
the examples.

There is no need to register tests. The registration is implicit
and happens with:

D's unittest` blocks

Functions with a camelCase name beginning with test (e.g. testFoo())

Classes that derive from TestCase and override test()

The modules to be reflected on must be specified when calling
runTests, but that's usually done as shown in the dub configuration
above. Private functions are skipped. TestCase also has support for
setup() and shutdown(), child classes need only override the
appropriate functions(s).

Don't like the algorithm for registering tests? Not a problem. The
attributes @UnitTest and @DontTest can be used to opt-in or
opt-out. These are used in the examples.
Tests can also be hidden with the @HiddenTest attribute. This means
that particular test doesn't get run by default but can still be run
by passing its name as a command-line argument. HiddenTest takes
a compile-time string to list the reason why the test is hidden. This
would usually be a bug id but can be anything the user wants.

Since D packages are just directories and there the compiler can't
read the filesystem at compile-time, there is no way to automatically
add all tests in a package. To mitigate this and avoid having to
manually write the name of all the modules containing tests,
a dub configuration called gen_ut_main runs unit-threaded as
a command-line utility to write the file for you.